body {
  font-family: "Poppins", sans-serif;
  background-color: #e8f0fe;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
}

.calculator {
  background-color: #fff;
  padding: 25px 30px;
  border-radius: 15px;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
  width: 320px;
  text-align: center;
}

h1 {
  font-size: 20px;
  color: #333;
  margin-bottom: 15px;
}

#display {
  width: 100%;
  height: 50px;
  font-size: 1.5em;
  text-align: right;
  padding: 10px;
  margin-bottom: 15px;
  border: 2px solid #ccc;
  border-radius: 8px;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}

.btn {
  background-color: #f2f2f2;
  border: none;
  padding: 15px;
  font-size: 1.2em;
  border-radius: 8px;
  cursor: pointer;
  transition: background 0.2s;
}

.btn:hover {
  background-color: #d9e4f5;
}

.operator {
  background-color: #ffce73;
}

.equal {
  background-color: #4caf50;
  color: #fff;
}

.clear {
  grid-column: span 4;
  background-color: #f44336;
  color: #fff;
  font-size: 1.1em;
}